Guide to SVT-AV1 Encoder API Initialization

This article provides a direct guide to initializing the SVT-AV1 (libsvtav1) video encoder using its C API. It details the essential structures and sequential function calls required to allocate encoder handles, configure encoding parameters, and initialize the encoder state to prepare for video compression.

Essential Structures

To initialize the SVT-AV1 encoder, you must work with two primary structures defined in the library’s headers:

  1. EbComponentType
    This is the component handle that represents the encoder instance. All subsequent API calls targeting the encoder will require a pointer to this handle.

  2. EbSvtAv1EncConfiguration
    This structure contains all the configuration parameters for the encoding process, such as video resolution, frame rate, bit depth, rate control mode, target bitrate, and preset speeds.

Sequential Initialization Steps and Functions

Initializing the SVT-AV1 encoder requires a strict four-step sequence of function calls.

Step 1: Initialize the Handle and Default Parameters

Before configuring the encoder, you must allocate the component handle and populate the configuration structure with default settings. This is achieved using the svt_av1_enc_init_handle function.

EbComponentType *svt_handle = NULL;
EbSvtAv1EncConfiguration svt_config;

EbErrorType return_error = svt_av1_enc_init_handle(&svt_handle, NULL, &svt_config);
if (return_error != EB_ErrorNone) {
    // Handle initialization handle error
}

Step 2: Configure Encoding Parameters

After receiving the default configuration, you must modify the fields of the EbSvtAv1EncConfiguration structure to match your input video properties and target output quality.

At a minimum, you must specify: * Source width and height (source_width, source_height) * Frame rate numerator and denominator (frame_rate_numerator, frame_rate_denominator) * Color format and bit depth (encoder_color_format, encoder_bit_depth)

svt_config.source_width = 1920;
svt_config.source_height = 1080;
svt_config.frame_rate_numerator = 60000;
svt_config.frame_rate_denominator = 1001;
svt_config.encoder_bit_depth = 8;
svt_config.encoder_color_format = EB_YUV420;

Step 3: Apply the Configuration Parameters

Once the configuration structure is updated, you must apply these parameters to the encoder handle using svt_av1_enc_set_parameter.

return_error = svt_av1_enc_set_parameter(svt_handle, &svt_config);
if (return_error != EB_ErrorNone) {
    // Handle parameter setting error
}

Step 4: Initialize the Encoder Instance

The final step is to initialize the encoder instance, which allocates the internal buffers, threads, and resources needed for the encoding pipeline. This is triggered by calling svt_av1_enc_init.

return_error = svt_av1_enc_init(svt_handle);
if (return_error != EB_ErrorNone) {
    // Handle final initialization error
}